Tenho as duas tabelas a seguir:

1. Lecturers (LectID, Fname, Lname, degree).
2. Lecturers_Specialization (LectID, Expertise).

Quero encontrar o professor com mais Especialização. Quando tento isso, ele não está funcionando:

SELECT
  L.LectID, 
  Fname, 
  Lname 
FROM Lecturers L, 
     Lecturers_Specialization S
WHERE L.LectID = S.LectID
AND COUNT(S.Expertise) >= ALL (SELECT
  COUNT(Expertise)
FROM Lecturers_Specialization
GROUP BY LectID);

Mas quando eu tento isso, ele funciona:

SELECT
  L.LectID,
  Fname,
  Lname 
FROM Lecturers L,
     Lecturers_Specialization S
WHERE L.LectID = S.LectID
GROUP BY L.LectID,
         Fname,
         Lname 
HAVING COUNT(S.Expertise) >= ALL (SELECT
  COUNT(Expertise)
FROM Lecturers_Specialization
GROUP BY LectID); 

Qual é a razão? Obrigado